In industrial alarm management, a false alarm could refer either to an alarm with little information content that can usually safely be eliminated, or one that could be valid but is triggered by a faulty instrument. Both types are problematic because of the "cry wolf" effect described above.
The term "false alarm" is actually a misnomer, and is regularly replaced by the term "nuisance alarm." When a sensor operates, it is hardly false, and it is usually a true indication of the present state of the sensor. A more appropriate term is nuisance, indicating that the alarm activation is inconvenient, annoying, or vexatious. A prime example of this difference is burglar alarms being set off by spiders. (A spider crawling on a web in front of the motion detector appears very large to the motion detector.)
One tragic example of the consequences of continued false alarms was at Boland Hall at Seton Hall University on January 19, 2000. Months of false alarms caused many students to start ignoring the fire alarms. However, when an actual fire broke out, three students who ignored the alarms died, and many others suffered injuries.
Likewise, after too many audible car alarms are found false, most people no longer pay attention to see whether someone is stealing a vehicle, so even certain experienced thieves may confess that these alarms would not deter them from stealing vehicles.
False alarms could also refer to situations where one becomes startled about something that is later determined to be untrue.